Surface maintenance machine drive

ABSTRACT

A mobile sweeping machine having separate hydraulic motors for driving the curb brush and the propulsion wheel; a battery powered, constant speed electric motor that through mechanical drive connections drives the main sweeping brush, the suction blower and tandem pump; and a control valve for selectively applying fluid under pressure from the fixed displacement tandem pump section to the curb brush, the cylinder for elevating the debris and filter receptacle, and to either of the curb brush and cylinder. The variable displacement pump section of the tandem pump supplies fluid under pressure to the propulsion wheel hydraulic motor. A filter is located in the return line ahead of the variable volume pump section.

United States Patent Kasper SURFACE MAINTENANCE MACHINE DRIVE [72] Inventor: Joseph G. Kasper, Minneapolis,

Minn.

[73] Assignee: Tennant Company,

Minn.

22 Filed: Oct. 30, 1970 [21] Appl.No.: 85,468

Minneapolis,

[56] References Cited UNITED STATES PATENTS 11/1950 Paulson ..15/82 1/1965 Lutz ..15/340 9/1965 Campbell ..15/83 X 1 Sept. 19, 1972 12/1965 Kaar et a1. ..15/83 X l/1968 Firth et. a1. ..60/53 R 5 7] ABSTRACT A mobile sweeping machine having separate hydraulic motors for driving the curb brush and the propulsion wheel; a battery powered, constant speed electric motor that through mechanical drive connections drives the main sweeping brush, the suction blower and tandem pump; and a control valve for selectively applying fluid under pressure from the fixed displacement tandem pump section to the curb brush, the cylinder for elevating the debris and filter receptacle, and to either of the curb brush and cylinder. The variable displacement pump section of the tandem pump supplies fluid under pressure to the propulsion wheel hydraulic motor. A filter is located in the return line ahead of the variable volume pump section.

13 Claims, 2 Drawing Figures SURFACE MAINTENANCE MACHINE DRIVE BACKGROUND OF THE INVENTION A self-propelled power driven surface maintenance machine, such as a sweeping machine, having hydraulically operated debris receptacle, propulsion wheel and a curb brush.

In the prior art, for example US. Pat. No. 3,165,775 to Lutz, there is disclosed a power sweeper having hydraulically operated curb brush, propulsion wheel and debris receptacle. In order to provide an effective, more simplified hydraulic system for surface cleaning machines, and a battery powdered surface cleaning machine of an efficiency similar to that obtained by a gasoline powered machine, as well as overcome other disadvantages of prior art machines, this invention has been made.

SUMMARY OF THE INVENTION A self-powered mobile surface maintenance machine having a curb brush, a receptacle for debris, lift arms for elevating the receptacle, a piston cylinder combination for operating the lift arms, a first hydraulic motor for driving the propulsion wheel, a second hydraulic motor for driving the curb brush, and a tandem pump driven by the motor. One pump section is of variable displacement type for driving the first hydraulic motor while the second pump section, through a control valve, selectively applies fluid under pressure to accessories such as the curb brush motor or the cylinder.

In many places it is highly desirable to use electric powered equipment in place of gasoline powered equipment, one reason being to cut down on pollution. At the same time there is the problem of obtaining an electrically powered machine that is about as economical to use as a gasoline powered vehicle without sacrificing the usability and performance of the vehicle.

With this invention, through the use of a single large electric motor there is available more horsepower for propelling the vehicle up grades, and a higher speed of travel than if there were provided one smaller electric motor for propelling the vehicle and one or more other electric motors for operating the main sweeping brush and accessories such as a curb brush. By using a single constant speed electric motor that drives hydraulic pumps, and using hydraulic controls, the electric motor is continuously used in its most efficient speed range while at the same time the speed of the vehicle may be varied and the suction blower and main brush may be driven at constant speeds. Additionally, no rheostat is required in the electric motor circuitry for varying the speed of the electric motor and accordingly electrical energy is not being needlessly expended and the electrical motor is not operated out of its most efficient range of speeds even though the speed of the vehicle is varied.

Using a variable displacement pump for driving the hydraulic motor for the propulsion wheel, the speed of travel can be controlled without pumping more hydraulic fluid than is needed. Also, through the use of an electric motor to drive the hydraulic pumps which drive hydraulic motors, hydraulic controls are used which provide for greater ease of control and maneuverability; and with the use of a hydraulic motor for driving the vehicle, more room is available on the vehicle for batteries. Also through the provision of the various features of the invention herein set forth, less battery capacity is required for a given period of normal usage of the machine than if these features were not provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustrative schematic view showing one form of a sweeping machine embodying the invention; and

FIG. 2 is a schematic of the variable volume pump section.

Referring to the drawings, and particularly to FIG. 1, the invention may be embodied in varying forms of sweeping machines, the exact physical configuration of which may be varied. Illustrative forms of machines, which may be used as a basic arrangement for embodying the invention, are illustrated in copending application Ser. No. 720,503, filed Apr. 11, 1968, and now US. Pat. No. 3,540,070 US. Pat. Nos. 2,972,159 and 3,186,021, and US. Pat. Nos. 3,189,931 and 3,160,908, which show in greater detail the mechanical configuration of the particular sweeping machine illustrated in the instant application. As the details of the mechanical structure of the sweeping machine may be varied, it is therefore to be understood that the particular machine herein described is merely illustrative and is not a limitation of the invention.

In FIG. 1 the machine, generally designated 10, includes a wheeled frame having front wheels 1 1 and a steering and propulsion wheel 12. The wheel 12 is supported on a suitable bracket 14 which is mounted in a vertical spindle 15 in the bearing 16, and the spindle is provided with a sidearm l7 and drag link 18, the drag link being connected to a suitable steering apparatus so that the wheel 12 can be turned about the axis of spindle 15 for steering motion. The bracket 14 which car ries the wheel also serves to support a hydraulic motor generally designated 20 which is attached by suitable bolts 21 to the outer surface of the bracket 14. The axle 22, on which wheel 12 is mounted, is directly coupled to the shaft of the motor 20.

On the sweeping machine frame 30 there is a transverse open bottom housing or enclosure 31 which serves to contain the cylindrical brush 32, which is mounted on radius rods, not shown, and is arranged to be driven by a belt drive 33 extending as herein illustrated by the dotted line 34, to a power take-off pulley 35 of constant speed electric motor 36. The enclosure 31 has an opening across its front. face, extending from sidewall to sidewall of the enclosure, and provided with a flexible gasket 37 all around.

The machine has a pivot shaft at 40 upon which a pair of forwardly extending support arms 41 are provided, the shaft 40 also being provided with a crank 42 which is coupled to the piston rod 44 of the hydraulic cylinder 45, the base of which is suitably pivoted on the machine frame. Hydraulic supply and return lines 46 and 47 serve this hydraulic cylinder. When pressure is introduced into the cylinder at port 43, the arms 41 will be swung up in the direction of arrow 48.

On the parallel arms 41 there is mounted a debris, dirt and dust receiving receptacle and filter unit generally designated 50. This unit consists of a dust and debris receiving pan 51 which is connected at the bracing 52 to a housing 53 containing dust filter equipment.

The upper part of the housing 53 is connected to a plenum chamber which is in communication with the top (clean) side of the filter within the housing 53. The plenum chamber has a suction outlet at 55 which seats upon a soft gasket 56 which surrounds a port 57 connected to the suction line 58. The port and suction line are on the frame of the machine proper. The suction line 58 connects with the inlet 59 of a suction blower 60 which is mounted on the machine frame. The suction blower is mechanically driven by any suitable mechanical drive 61 from a second power output pulley 63 of motor 36.

The filter 62 in housing 53 serves to remove the dust from the air, and the dust residue falls into the pan 51. The pan 51 has a rearwardly extending mouth portion 64 which fits into the opening in the front part of the sweeping housing 31, being sealed thereto by the soft gasket 37. The brush 32 revolves clockwise as shown in FIG. 1, and sweeps dirt, debris, and dust in the direction of arrow 65 into the pan 51, where the heavier particles of dirt and debris accumulate. The dust, carried by the air which also enters the mouth 64 of the pan from the sweeping housing 31, follows the of arrows 66 and after passing up through the filter 62, where the air is cleaned, the clean air continues its travel at 67 through the plenum chamber 54 and thence enters the port 57 and tube 58 as shown by arrow 68 and continues through tube 58 to the inlet of the suction blower 60.

Pivoted at 75 on the machine frame is a forwardly extending arm 76 which serves as a mounting for hydraulic motor 77, the output shaft 78 of which extends downwardly and carries an auxiliary brush such as a curb brush 79. Hydraulic lines 80 and 81 serve as pressure and return lines respectively for the hydraulic motor.

The drive shaft of motor 36 is mechanically coupled to the shaft 91 of the tandem pumps 92, 93 to drive the pumps. Pumps 92, 93 include a variable displacement piston type pump section 92 which through a closed circuit drives motor 20. That is, line 70 is connected to port 128 of pump section 92 and line 71 is mounted to port 129. Pump section 92 has a swash plate control 92a to regulate the amount of fluid under pressure being pumped to motor 20 and accordingly regulates the speed of movement of the vehicle; pump section 92 being of an overcenter type that provides for reverse flow to motor 20 and thereby for reverse rotation of motor 20 as well as a neutral or a stopped position. Pump section 92 includes a variable displacement pump member 150 having the swash plate control 92a and internal circuitry that includes a line 152 connecting port 129 to port 151a of pump member 150, a line 153 connecting port 128 to port 151b of pump member 150, a line 155 connecting pump member port 151d to port 110 and a line 154 connected to port 151a of pump member 150. Ports 1510, 151d are in constant fluid flow communication through a fluid passageway in the pump member 150.

A line 158 is connected to line 154 and to a port on high pressure relief valve member 159 to receive fluid when the valve is open and the quantity of fluid to be by-passed is greater than that which will flow through line 161, spring member 159a acting to retain valve member in a closed position until a predetermined pressure in line 160 has been exceeded. Lines 161, 162 are connected to ports of valve 159 to be placed in fluid communication with one another through valve 159 upon the opening of valve member 159b, line 161 being connected to port 94. Lines 163, 164 are connected to ports of valve 167 to be placed in fluid communication through valve 167 upon the opening of valve member 167a of valve 167. Valve member 167a is spring biased by spring 165 to a closed position while a line 166 connects line 161 to a port of valve 167 for applying fluid under pressure to open valve member 167a. Valve 167 is a low pressure relief valve, for example opens when the pressure in line 166 exceeds 50 psi while valve 159 is a higher pressure valve, for example open when the pressure in line 160 exceeds 3,000 psi. Line 163 is connected to line 161 while line 164 is connected to line 155.

A line having a check valve 170 therein blocks fluid flow from line 153 to line 161 while permitting fluid flow in the opposite direction when the pressure is higher in line 161 than in line 153. Similarly, a line having a check valve 171 therein blocks fluid flow from line 152 to line 161 while permitting fluid flow in the opposite direction when the pressure is higher in line 161 than in line 152. A line having a check valve 172 therein blocks fluid flow from line 162 to line 152 while permitting fluid flow in the opposite direction when fluid pressure is higher in line 152 than line 162; whereas a line having a check valve 173 therein blocks fluid flow from line 162 to line 153 but permits fluid flow in the opposite direction when the pressure is higher in line 153 then in line 162.

A bypass valve 175 places line 162 in fluid communication with line 154 when its valve member 175a is opened; the fluid pressure applied from line 177 acting against spring member 175b to move valve member 175a to an open position to directly bypass fluid when a surge in pressure is about the same as that which opens valve 159. Line 177 is connected to line 176 which in turn is connected to line 162.

There is provided a soft ride valve that includes a valve 180 having a valve member 18% that in an open position fluidly connects line 176 to line 181, which in turn is connected to line 154. A line 182 connects line 176 to valve 180 for applying fluid under pressure to open valve member 180k against the action of spring member 180c. Line 184 permits fluid flow between valve 180 and accumulator 188 when valve member 1801) is open. A flow restrictor 185 is connected across lines 176, 184 while the accumulator 188 is connected to line 184, to receive fluid from line 184 and discharge fluid thereto. A leakage line 187 connects the accumulator to line 181. The accumulator is of a type that the piston 188a is spring urged to exhaust fluid received from line 184 back to line 184, while the flow restrictor 185 restricts the rate of flow between lines 176, 184. Thus pump section 92 also has internal circuitry 92b fluidly connected between ports 94, 110 that permits flow of fluid therethrough regardless of the position of control 92a and provides makeup fluid to closed circuit for driving motor 20 to compensate for any leakage loss and the like in the fluid circuit of and for driving motor 20.

Pumps 92, 93 also include a fixed displacement pump section 93. Since pumps 92, 93 are conventional pumps, for example, made and sold by the Vickers Mobile Division of the Sperry Rand Corporation under the trade designation TA6Vl0, they will not be further described. It is to be understood that pumps 92, 93 may be two adjacent pumps having their shafts mechanically coupled together, or each mechanically coupled to the electric motor shaft so as to function the same as pumps 92, 93 as herein described, and thus pump sections 92, 93 may be considered as two separate pumps. The pump inlet 94 of pump section 92 is connected by a line 95 to the filter 96 which in turn is connected by a line 97 to the junction 98. Junction 98 is fluidly connected to line 81 and line 99. Line 99 is fluidly connected to the port 101 of the three position control valve, generally designated 100. A second port 102 of the valve is fluidly connected by a line 103 to the outlet port 104 of pump section 93. A line 105 fluidly connects the inlet port 107 of pump section 93 to a port 108 on the lower part of the sump 109 while port 112 of the sump is connected by a line 111 to the outlet port 110 of the pump section 92. A third port 113 of the sump has line 46 connected thereto.

Valve 100 has a third port 118 fluidly connected to line 80, a port 119 fluidly connected to line 47, and a valve member 120. The valve member has a fluid passageway 122 that in a first position fluidly connects port 101 to port 102 but that does not open to either of the other ports. In a second position, the fluid connection between ports 101, 102 is broken, however, the fluid passageway 123 of the valve member fluidly con- .nects port 102 to port 119 and the fluid passageway 124 fluidly connects port 101 to port 118. In a third position, the fluid passageway 125 of the valve member fluidly connects port 102 to port 118 while the fluid passageway 12 6 flu idly connects port 101 to port 119.

Passageway 126 is of a shape that when the valve member is moved adjacent to its third position, it will establish a fluid connection between ports 101, 119 prior to passageway 125 fluidly connecting port 102 to port 118. As a result, the hopper may be lowered prior to the time that the curb brush is actuated.

As previously indicated, line 70 is fluidly connected to the port 128 of pump section 92 while line 71 is fluidly connected to the port 129 of pump section 92. It is to be noted that pump section 92 is of a construction that by shifting the control member 92a thereof between three positions, in one position no fluid under pressure is applied to either line 70 or 71; in a second position, fluid under pressure is applied to line 70 while line 71 serves as a return line, and in a third position fluid under pressure is applied 2line 70 serves as a return line. Thus, the drive for the motor is a closed hydraulic system other than for the provision for makeup fluid.

For controlling energization of the motor 36, line 139 connects one motor terminal to contact 142 of a first relay while a second contact 143 of the relay is connected by a line 144 to junction 145. A normally open switch member 146 upon energization of the relay coil 147 of the first relay electrically connects contacts 142, 143. One or more electrical batteries 148 are connected across junctions 141, 145; junction 141 being connected by a line 140 to the terminal of motor 36.

A line connects junction 14] to junction 250, a seat switch 251 and the coil 252 of a second relay being connected in series across junctions 250, 153. The seat switch is of a type that is resiliently retained in an open position, however, it is closed as long as the operator sits on the seat 149 of the vehicle. Coil 147 is connected across junction 250 and contact 254 of the second relay, the second relay having a contact 255 that is connected by a line to junction 156, a third contact 157 that is connected by a line to junction 156, and a fourth contact 258 that is connected by a line to junction 253. Upon energization of coil 252, switch member 259 moves to electrically connect contact 254 to contact 255 and switch member 260 moves to electri'cally connect contact 157 to contact 258. A start switch 261 which is resiliently retained in an opened condition is connected across junctions 253, 262, lines connecting junction 262 to junction 145 and 156. When the operator sits on the seat, switch 251 is closed and upon depressing switch 261, relay 252 is energized whereby switch member 260 forms a hole-in circuit to retain the relay energized even though switch 261 moves to an opened condition. At this time switch member 259 is closed to energize coil 147 whereby switch member 146 completes a circuit for energizing the motor 36. The seat switch provides a safety feature wherein the motor is de-energized if the operator is off the seat.

When motor 36 is energized and the valve is in its first position, no fluid under pressure is applied either to curb brush 79 or to the cylinder 45. Upon operating control lever 264 for moving the valve member to its third position, fluid under pressure from port 104 passes trough the valve and line 80 to the curb brus'li motor for operating the curb brush, it being noted at this time that it is not possible to apply fluid under pressure to cylinder 45 for moving the lift arms in the direction of arrow 48.

By moving control 92a in the appropriate direction, fluid under pressure is applied to motor 20 for propelling the vehicle, the speed and direction (forward or reverse) of movement of the vehicle being dependent upon the position of the control 92a. The further the control 92a is moved in the direction of arrow 265 from its neutral position, the higher the volume of fluid applied to motor 20 for propelling the vehicle; and accordingly, the higher the speed that is obtained.

When the receptacle or hopper 50 is to be elevated or emptied, control 264 is operated to move valve member 120 to its second position whereby fluid under pressure from port 104 is applied through passageway 123 to the end of the cylinder 45 for operating the lift arm in the direction of the arrow 48; however, at this time, no fluid under pressure is applied to the curb brush motor. After the hopper has been emptied, valve member 120 is again operated to its third position whereby line 47 is connected to the return line 99 through passageway 126. Accordingly, due to the weight of the hopper, arms 41 rotate in the direction opposite arrow 48.

In the event that a vehicle is to go up a steep grade, the valve member 120 is operated to its first position whereby the load on pump section 93 is cut to a minimum. Further, since motor 36 is an electric motor,

it may be operated above its rated capacity for a short period of time whereby greater power can be obtained for driving the pump section 92 for propelling the vehicle. That is, through the provision of an electric motor driving the tandem pump, the control valve may be operated to its first position and a reserved capacity is provided for driving the vehicle for a short period of time. For example, if the vehicle is going up a sharp incline and motor 36 is a 4 horsepower motor, by having the control valve in its first position, three horsepower is available to drive the vehicle. For a short period of time the motor can be overloaded to 2-50 percent which provides 7 horsepower to drive the vehicle.

By using an electric motor that drives a variable displacement pump which in turn drives the hydraulic propelling motor 20, no electrical variable speed controls have to be provided in the electrical control circuitry; and accordingly losses are minimized in comparison to if an electrical variable speed control was used. Additionally, through the controls described, the electric motor is operated at an efficient speed whereas, if the speed of the electric motor had to be varied to control the speed of the vehicle, the electric motor frequently would be operated at inefficient speeds.

With the hydraulic system of this invention the filter is provided in the return line whereby any makeup fluid to pump section 92 is filtered, and at the same time an output pressure up to 2,500 psi may be obtained from pump section 93.

When pump section 93 is being driven and valve 100 is in its first, or second, or third position, and the, fluid pressure in line 153, or 152, is below that in line 161, for example from loss of fluid in lines 153, 152, the respective one of check valves 170, 171 permits flow fluid from line 161 to lines 153 or 152 until the pressure is substantially the same as that in line 161. Thus valve 167 maintains a pressure in line 161 for providing makeup fluid to lines 152, 153 and for operating motor 77 and piston cylinder 44, 45.

When there is a surge in pressure in line 152, or line 153, check valve 172, or 173, respectively will open to permit passage of fluid to line 162. If the pressure exceeds the setting of valves 159, 175 they will open to bypass fluid. After the initial surge has passed, valves 159, 175 close. During the initial surge and after valves 159, 175 close the soft ride valve permits fluid discharge to line 181 until the pressure in line 162 is about the normal operating pressure for the pressurized line oflines 152, 153.

What is claimed is:

1. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a reversible variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for directly conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, a sump for containing hydraulie fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump.

2. The apparatus of claim 1 further characterized in that said pumps are tandem pumps having the first pump as a first pump section and the second pump as a second pump section.

3. The apparatus of claim 1 further characterized in that the third means includes control valve means for selectively controlling the application of fluid under pressure from the second pump to the cylinder means and second motor means, return line means between the sump and the control valve means and second motor means for returning fluid from the control valve means and second motor means to the sump and a filter in the return line means between the control valve means and the sump.

4. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, the third means including a three position control valve having a first, a second, a third and a fourth port, a pressure fourth line for conducting fluid under pressure from the second pump to the second port, a pressure fifth line for fluidly connecting the third port to the second motor means, a pressure sixth line for fluidly connecting the fourth port to the piston cylinder means for applying fluid under pressure thereto, and a return seventh line fluidly connecting the first port to the sump, said control valve including a valve member movable between a first position fluidly connecting the first and second ports, a second position fluidly connecting the first port to the third port and the second port to the fourth port, and a third position fluidly connecting the first port to the fourth port and the third port to the second port.

5. The apparatus of claim 4 further characterized in that there is provided a battery, a seat, a seat operated switch, and circuit means for interconnecting the battery, the switch and the motor to pennit energizing the motor when the operator sits on the seat.

6. The apparatus of claim 4 further characterized in that the first pump has internal circuitry forming a part of the return seventh line and that a filter is provided in the seventh line between said internal circuitry and the first port.

7. The apparatus of claim 6 further characterized in that the third means includes a return line that fluidly connects the second motor means to the return seventh line between the filter and the second port and a return line that fluidly connects the cylinder means to the sump.

8. A surface maintenance machine having a frame, propulsion and steering wheels mounted on the frame, a debris receptacle, a brush mounted on the frame for directing material from the surface to be maintained to the receptacle, lift arm means mounted on the frame for carrying the receptacle adjacent the brush and alternately lifting the receptacle, pistoncylinder means for operating the arm means to lift the receptacle, a sump, hydraulic motor means for driving the propulsion wheel, a tandem pump having a reversible, overcenter type variable displacement first pump section and a second pump section, a constant speed motor, mechanical means for drivingly coupling the motor to the pump, mechanical means for drivingly connecting the motor to the brush, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, a third line connectedbetween the sump and the second pump section to supply fluid to the second pump section, and third means for selectively applying fluid under pressure from the second pump section to piston cylinder means and returning fluid to the sump.

9. The apparatus of claim 8 further characterized where the first and second lines conduct fluid directly from the first pump section to the first motor means and directly from the first motor means to the first pump section, and that said first pump section has internal means forming a part of the third means for supplying make-up fluid to that which flows through the first and second lines.

10. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, the first pump having an internal circuit forming part of the return line means and supplying makeup fluid to the first pump to compensate for loss of fluid in the first motor means and the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, said third means including control valve means for selectively controlling the application of fluid under pressure form the second pump to the cylinder means and second motor means, return line means between the sump and thecontrol valve means and second motor means for returning fluid from the control valve means and second motor means to the sump and a filter in the return line means between the control valve means and the sump.

11. A surface maintenance machine having a frame, propulsion and steering wheels mounted on the frame, a debris receptacle, a brush mounted on the frame for directing material from the surface to be maintained to i the receptacle, lift arm means mounted on the frame for carrying the receptacle adjacent the brush and alternately lifting the receptacle, piston cylinder means for operating the arm means to lift the receptacle, a sump, hydraulic motor means for driving the propulsion wheel, a tandem pump having a variable displacement first pump section and a second pump section, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pump, mechanical means for drivingly connecting the motor to the brush, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, the first pump section including pump means having internal means forming a part of the third means for supplying makeup fluid to that which flows through the first and second lines, a third line connected between the sump and the second pump section to supply fluid to the second pump section, and third means for selectively applying fluid under pressure from the second pump section to piston cylinder means and returning fluid to the sump, the third means having a line between the cylinder means and the internal means including a filter and a line from the internal means to the sump to return hydraulic fluid to the sump.

12. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, first hydraulic motor means for driving the propulsion wheel, second hydraulic motor means for driving the auxiliary brush, a tandem pump having a variable displacement first pump section and a second pump section, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pump, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump section, third means for connecting the second pump section to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, a battery, a seat operated switch, a nonnally opened, manually operated switch and a first relay con nected in series with said switches and said battery, and circuit means connected to said battery and motor for energizing the motor upon the relay being energized.

13. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a reversible variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first thereto and return fluid to the sump, said first pump having an internal circuit forming part of the return line means and supplying makeup fluid to the first pump to compensate for loss of fluid in the first motor means and the first pump.

PO-IW UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Dated September 19, 1972 Patent No. 3 ,691I579 Invontor(s) Joseph G. Kasper It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 62, "hydraulic" should be --hydraulic--.

Column 5, line 54, delete "Zline 70" and add --to line 71 while line 70--.

Signed and sealed this 6th day of February 1973.

(SEAL) Attest:

ROBERT GOTTSCHALK EDWARD M.FLETCHER,JR. Attesting Officer Commissioner of Patents 

1. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a reversible variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for directly conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump.
 2. The apparatus of claim 1 further characterized in that said pumps are tandem pumps having the first pump as a first pump section and the second pump as a second pump section.
 3. The apparatus of claim 1 further characterized in that the third means includes control valve means for selectively controlling the application of fluid under pressure from the second pump to the cylinder means and second motor means, return line means between the sump and the control valve means and second motor means for returning fluid from the control valve means and second motor means to the sump and a filter in the return line means between the control valve means and the sump.
 4. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, the third means including a three position control valve having a first, a second, a third and a fourth port, a pressure fourth line for conducting fluid under pressure from the second pump to the second port, a pressure fifth line for fluidly connecting the third port to the second motor means, a pressure sixth line for fluidly connecting the fourth port to the piston cylinder means for applying fluid under pressure thereto, and a return seventh line fluidly connecting the first port to the sump, said control valve including a valve member movable between a first position fluidly connecting the first and second ports, a second position fluidly connecting the first port to the third port and the second port to the fourth port, and a third position fluidly connecting the first port to the fourth port and the third port to the second port.
 5. The apparatus of claim 4 further characterized in that there is provided a battery, a seat, a seat operated switch, and circuit means for interconnecting the battery, the switch and the motor to permit energizing the motor when the operator sits on the seat.
 6. The apparatus of claim 4 further characterized in that the first pump has internal circuitry forming a part of the return seventh line and that a filter is provided in the seventh line between said internal circuitrY and the first port.
 7. The apparatus of claim 6 further characterized in that the third means includes a return line that fluidly connects the second motor means to the return seventh line between the filter and the second port and a return line that fluidly connects the cylinder means to the sump.
 8. A surface maintenance machine having a frame, propulsion and steering wheels mounted on the frame, a debris receptacle, a brush mounted on the frame for directing material from the surface to be maintained to the receptacle, lift arm means mounted on the frame for carrying the receptacle adjacent the brush and alternately lifting the receptacle, piston cylinder means for operating the arm means to lift the receptacle, a sump, hydraulic motor means for driving the propulsion wheel, a tandem pump having a reversible, overcenter type variable displacement first pump section and a second pump section, a constant speed motor, mechanical means for drivingly coupling the motor to the pump, mechanical means for drivingly connecting the motor to the brush, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, a third line connected between the sump and the second pump section to supply fluid to the second pump section, and third means for selectively applying fluid under pressure from the second pump section to piston cylinder means and returning fluid to the sump.
 9. The apparatus of claim 8 further characterized where the first and second lines conduct fluid directly from the first pump section to the first motor means and directly from the first motor means to the first pump section, and that said first pump section has internal means forming a part of the third means for supplying make-up fluid to that which flows through the first and second lines.
 10. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, the first pump having an internal circuit forming part of the return line means and supplying makeup fluid to the first pump to compensate for loss of fluid in the first motor means and the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, said third means including control valve means for selectively controlling the application of fluid under pressure form the second pump to the cylinder means and second motor means, return line means between the sump and the control valve means and second motor means for returning fluid from the control valve means and second motor means to the sump and a filter in the return line means between the control valve means and the sump.
 11. A surface maintenance machine having a frame, propulsion and steering wheels mounted on the frame, a debris receptacle, a brush mounted on the frame for directing material from the surface to be maintained to the receptacle, lift arm means mounted on the frame for carrying the receptacle adjacent the brush and alternately lifting the receptacle, piston cylinder means for operating the arm means to lift the receptacle, a sump, hydraulic motor means for driving the propulsion wheel, a tandem pump having A variable displacement first pump section and a second pump section, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pump, mechanical means for drivingly connecting the motor to the brush, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, the first pump section including pump means having internal means forming a part of the third means for supplying makeup fluid to that which flows through the first and second lines, a third line connected between the sump and the second pump section to supply fluid to the second pump section, and third means for selectively applying fluid under pressure from the second pump section to piston cylinder means and returning fluid to the sump, the third means having a line between the cylinder means and the internal means including a filter and a line from the internal means to the sump to return hydraulic fluid to the sump.
 12. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, first hydraulic motor means for driving the propulsion wheel, second hydraulic motor means for driving the auxiliary brush, a tandem pump having a variable displacement first pump section and a second pump section, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pump, first and second lines for conducting hydraulic fluid under pressure from the first pump section to the first motor means and return fluid from the first motor means to the first pump section, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump section, third means for connecting the second pump section to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, a battery, a seat operated switch, a normally opened, manually operated switch and a first relay connected in series with said switches and said battery, and circuit means connected to said battery and motor for energizing the motor upon the relay being energized.
 13. A surface maintenance machine having propulsion and steering wheels, a debris receptacle, lift arm means for carrying the receptacle, piston cylinder means for operating the arm means to lift the receptacle, an auxiliary brush, hydraulic motor first means for driving the propulsion wheel, hydraulic motor second means for driving the auxiliary brush, a reversible variable displacement first pump, a second pump, a constant speed electric motor, mechanical means for drivingly coupling the motor to the pumps to drive the pumps, first and second lines for conducting hydraulic fluid under pressure from the first pump to the first motor means and return fluid from the first motor means to the first pump, a sump for containing hydraulic fluid, a third line for conducting fluid from the sump to the second pump, and third means for connecting the second pump to the second motor means and piston cylinder means to selectively apply fluid under pressure thereto and return fluid to the sump, said first pump having an internal circuit forming part of the return line means and supplying makeup fluid to the first pump to compensate for loss of fluid in the first motor means and the first pump. 